Western dwarf mistletoe (Arceuthobium campylopodum) can be
a serious parasite of pines in campgrounds as well as in timber-
producing forests. To measure dwarf mistletoe-related mortality of
ponderosa and Jeffrey pines, we collected infection
intensity and tree vigor data at five forested campgrounds in
southern and northeastern California and on the Nevada shore of Lake
Tahoe. Annual mortality over eight years was compared to mistletoe
infection class [Hawksworth 7-class dwarf mistletoe rating
(DMR)] , radial growth, and age at death. Overall, 7% (206) of
the pines died of natural causes on all five plots. The proportion of
trees killed increased with the severity of infection: by the end of
the survey, 3% of the uninfected [DMR 0], 4% of the slightly-
infected [DMR 1-2], 7% of the moderately-infected [DMR
3-4], and 22% of the severely-infected [DMR 5-6] pines
had died. Cambium-feeding insects, including bark beetles, pine
engravers, and flatheaded borers, were involved in the deaths of all
but one of the pines. More than 80% of the trees that died were
slow-growing (10-year radial growth 10 mm or less) and younger than
100 years of age. We discuss the differences in dwarf mistletoe
intensity, stand vigor, and pattern of mortality at each of the
campgrounds, and consider the implications of these results for
campground management.